Patent GB-668323-A (GB)
Title: Improvements in percussion drills for deep boring
IPC: E21B4/06
Filed: 1949-06-16
Abstract: 668,323. Percussive drills for well boring. MAZALAN PAL BANYAMEBNOK MELYFURASI VALLALATA ES GEPGYARA. June 16, 1949. [June 17, 1948] No. 16112/49. Class 85. A percussion drill for well boring driven by flush water acting on a cushioned hollowed piston carrying the cutter bit is characterised in that the cut-off members which alternatively admit and stop the flush water from passing the piston are positively controlled by impact feelers associated with the tool, The percussion bit 30 is screwed onto a tube 29 that slides in a fixed cylinder 28 and has an enlarged cavity 34 formed therein which is connected to the bore 39 of the tube and contains two hinged valves 35, 36 which are biased by springs 37 to be in a closed position so that the passage of the flush water through the bore 39 to the bore in the bit is obstructed and the consequent build up in pressure forces the tube 29 and the associated bit downwards against a spring. Two feeler rods 52 pass through the bit and project below the bit so that, as the bit at the end of the stoke slides relative to the rods, the wedge 45 carried by the rods forces the valves apart and locks them in the open position to allow the flush water to escape freely and the springs to return the tube 29 and bit ready for the next stroke. To reduce resistance of the flush-water to the opening of the valves, ports 40-43 lead from the valve chamber through the side walls of the bit or through the back portions of the valves. To free the wedges 45 from the valves for the return stroke, extensions 51 of the rods 52 abut against the fixed cylinder so that the bit rises relative to the rods. To enlarge the bottom of the bore, an annular bit is fitted over the end of the main bit, the annular bit comprising two pivotally connected sections 63, 64 spring biased so as to normally be in the extended position, said bit being attached to the bit body by springs and levers 72, 73. To take up the thrust of the drill in the bore, spring biased shoes 86 secured to the fixed drill body engage the walls of the bore and may have ports therein for pumping out grout. The shoes can be contracted by slidable latching arrangements. The drill can be given intermittent rotation either by spiral ribbing on the piston stem or by varying the length of the pivot levers 87, 88. The Specification, as open to inspection under Sect. 91, describes also a second embodiment in which a piston carrying the bit is blanked off at the central portion thereof and has three groups of ports formed therein, whilst in the upper portion is a sleeve having two groups of ports. The piston slides within a cylinder, downward motion being opposed by a spring. On the down stroke, flush water can pass through the ports and act on the blanking-off portion of the tube to force the tube down until at the end of the stroke a portion of the bit freely movable with a projecting below the main portion of the bit engages the bottom of the bore and relative movement occurs between the rest of the downwardly-moving parts and rods which are supported by that portion of the bit projecting, below the main portion of the bit. These rods support a ring on which is formed a cam surface over which rides a pip on the piston so that the piston tube is caused to rotate until discharge ports can be brought into alignment to permit the flush water to escape and allow the bit to return upwards until a cam surface rotates the piston tube to close off the exhaust ports. This subject-matter does not appear in the Specification as accepted.